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once-crowded school has become an intimate one.
    Would you send your child to Shepaug Valley Middle School?

2.
    The story of Vivek Ranadivé and the Redwood City girls’ basketball team suggests that what we think of as an advantage and as a disadvantage is not always correct, that we mix the categories up. In this chapter and the next, I want to apply that idea to two seemingly simple questions about education. I say “seemingly” because they seem simple—although, as we will discover, they are really anything but.
    The Shepaug Valley Middle School question is the first of the two simple questions. My guess is that you’d be delighted to have your child in one of those intimate classrooms. Virtually everywhere in the world, parents and policymakers take it for granted that smaller classes are better classes. In the past few years, the governments of the United States, Britain, Holland, Canada, Hong Kong, Singapore, Korea, and China—to name just a few—have all taken major steps to reduce the size of their classes. When the governor of California announced sweeping plans to reduce the size of his state’s classes, his popularity doubled within three weeks. Inside of a month, twenty other governors had announced plans to follow suit, and within a month and a half, the White House announced class-size reduction plans of its own. To this day, 77 percent of Americans think that it makes more sense to use taxpayer money to lower class sizes than to raise teachers’ salaries. Do you know how few things 77 percent of Americans agree on?
    There used to be as many as twenty-five students in a classroom at Shepaug Valley. Now that number is sometimes as low as fifteen. That means students at Shepaug get far more individual attention from their teacher than before, and common sense says that the more attention children get from their teacher, the better their learning experience will be. Students at the new, intimate Shepaug Valley ought to be doing better at school than students at the old crowded Shepaug—right?
    It turns out that there is a very elegant way to test whether this is true. Connecticut has a lot of schools like Shepaug. It’s a state with many small towns with small elementary schools, and small schools in small towns are subject to the natural ebbs and flows of birthrates and real-estate prices—which means that a grade can be all but empty one year and crowded the next. Here are the enrollment records, for example, for the fifth grade in another Connecticut middle school:
    1993   18
    1994   11
    1995   17
    1996   14
    1997   13
    1998   16
    1999   15
    2000   21
    2001   23
    2002   10
    2003   18
    2004   21
    2005   18
    In 2001, there were twenty-three fifth graders. The next year there were ten! Between 2001 and 2002, everything else in that school remained the same. It had the same teachers, the same principal, the same textbooks. It was in the same building in the same town. The local economy and the local population were virtually identical. The only thing that changed was the number of students in fifth grade. If the students in the year with a larger enrollment did better than the students in the year with a smaller one, then we can be pretty sure that it was because of the size of the class, right?
    This is what is called a “natural experiment.” Sometimes scientists set up formal experiments to try and test hypotheses. But on rare occasions the real world provides a natural way of testing the same theory—and natural experiments have many advantages over formal experiments. So what happens if you use the natural experiment of Connecticut—and compare the year-to-year results of every child who happens to have been in a small class with the results of those who happened to have come along in years with lots of kids? The economist Caroline Hoxby has done just that, looking at every elementary school in the state of Connecticut, and here’s what she found: Nothing! “There are